Method of manufacturing a permanent magnet

ABSTRACT

METHOD OF MANUFACTURING A M5R MAGNET HAVING A VERY HIGH COERCIVE FORCCE (M IS A RARE EARTH METAL OR TH OR A COMBINATION THEREOF; R IS CO OR CO COMBINED WITH ONE OR MORE OF THE ELEMENTS FE, NI AND CU) BY SINTERING BETWEEN 800*C AND 1100* C. IN THE PRESENCE OF AN OXYGEN GETTER, EXAMPLES OF SUCH AN OXYGEN GETTER ARE Y, TH, CA, ZR, GD AND CE.

United States Patent 3,701,695 METHOD OF MANUFACTURING A PERMANENT MAGNET Kurt Heinz Jiirgen Buschow and Frans Frederik Westendorp, Emmasingel, Eindhoven, Netherlands, assignors to US. Philips Corporation, New York, N.Y. No Drawing. Filed Apr. 28, 1970, Ser. No. 32,701 Claims priority, applicatisgnwlzlsgherlands, May 14, 1969,

Int. Cl. H01f 1/08 US. Cl. 148-103 5 Claims ABSTRACT OF THE DISCLOSURE Method of manufacturing a M R magnet having a very high coercive force (M is a rare earth metal or Th or a combination thereof; R is Co or C0 combined with one or more of the elements Fe, Ni and Cu) by sintering between 800" C. and 1100 C. in the presence of an oxygen getter. Examples of such an oxygen getter are Y, Th, Ca, Zr, Gd and Ce.

The invention relates to a method of manufacturing a permanent magnet of fine particles having permanentmagnetic properties, the essential constituent of which is a compound of a hexagonal structure whose existence range is integral with the existence range of the compound M R of the system MR, in which M is Co or a combination of Co with one or more of the elements Fe, Ni and Cu and R is one or more of the elements of the rare earth metals and/or Th, a solid body being made by sintering from a powder of permanent-magnetic particles of one or more compounds of M and R.

The element Y in this connection is also considered to belong to the rare earths.

Such a method is known, for example, from Dutch patent application No. 6807894 laid up for public inspection. The resultant permanent magnets may be magnetically isotropic or anisotropic according as the permanent-magnetic particles have been or have not been orientated prior to sintering.

In the aforesaid publication no examples are given from which details of the sintering process can be derived. It is neither stated which are the magnetic properties of the permanent magnets finally obtained by sintering of the; fine particles.

It has experimentally been found that permanent magnets consisting of sintered fine particles of the kind set forth have satisfactory permanent-magnetic properties if during the sintering process a combination of very specific conditions is satisfied: the sintering temperature has to be chosen in a specific temperature range and sintering has to be performed in an inert atmosphere.

For example, a basic powder containing SmCo and SIHzCOq subsequent to orientation in a magnetic field was sintered at 1050 C. for one hour in a He-atmosphere. After sintering the sole compound of Sn and Co left was found to be the permanent-magnetic compound SmCo The resultant body was found to have the following permanent-magnetic properties:

H =11,200 oersted B,=6,000 G The method according to the invention is characterized in that sintering is carried out at a temperature lying between -800 C. and 1200 C. in an inert atmosphere in the presence of a material readily binding reactive gasses, such as oxygen, after which the body obtained is cooled and magnetized in a magnetic field.

Surprisingly it has been found that if during sintering such a getter is present the coercive force of the resultant magnetic body is considerably higher. Examples of such getters" are Y, Th, Zr, Gd, Ca and rare earths elements.

Sintered bodies made from the same basic powder as mentioned above, which have first been orientated and have subsequently been sintered at 1050 C. in a He-atmosphere for one hour, showed H -values which considerably exceeded 11,200 oe. attained in sintering without a getter. The resultant higher values of coercive force are mentioned in the following table. This table also indicates which getter is used during sintering.

Sintering had been carried out in the presence of Y. Permanent magnets having such high coercive forces are particularly important in uses in which the magnet is exposed to high demagnetizing fields. The invention therefore also relates to a permanent magnet manufactured by the method in accordance with the invention.

We claim:

1. A method of manufacturing a permanent magnet comprising the steps of compacting into a body of given shape and dimensions, a mass of finely-divided material consisting of particles having permanent magnet properties and the essential constituent of which is a compound having a a hexagonal structure and whose existence range is integral with the existence range of the compound M R of the system MR, wherein M is an element selected from the group consisting of cobalt iron, nickel and copper and always includes cobalt and R is an element selected from the group consisting of the rare earths and thorium, and heating said body to a temperature between 800 C. and 1200 C. in an inert atmosphere in the presence of a getter consisting of an element selected from the group consisting of Y, Ce, La, Th, and Ca to sinter said body into a highly-coherent body having a greater coercive force H,) than a like body prepared in like manner in the absence of a getter, thereafter cooling said body and magnetizing said body.

2. A method as claimed in claim 1 in which R is Sm and M is Co.

3. A method as claimed in claim 2 in which the body is heated at a temperature between 1025 C. and 1100 C.

4. A method as claimed in claim 3 in which the inert atmosphere is He.

3 4 5. A method as claimed in claim 4 in which the getter OTHER REFERENCES Westendorp, F. F., et al., Permanent Magnets With References Cited Energy Products of 20 Million Gauss Oersteds, Solid UNITED STATES PATENTS 6 State Communications, 1969, pp. 639-40. 2 54 320 19 R 2 BUSChOW, K. H. 1., Intermetallic Compounds in the 3,051,566 3/1962 g g 73 5% System Samardium-Cobalt, Journal of the Less Common 3,378,671 4/1968 Harrison et al. 75-4755 x Metals, 3, 1968 P- 3,424,578 1/1969 Strnat et a1. 75-213 Prlmary EXamlner 3,546,030 12/ 1970 Buschow et al 148-103 X G. K. WHITE, Assistant Examiner FOREIGN PATENTS US. Cl. X.R.

663,067 12/1951 Great Britain 75-223 75200, 208, 223, 224; 148-101 

